1. Field of the Invention
The present invention relates to the field of metropolitan area network (MAN) topologies and internetwork communications technologies. In particular, the present invention relates aggregating multiple virtual local area networks (VLANs) into a MAN using VLAN identifier (VLAN ID) exchange.
2. Background Information and Description of Related Art
A metropolitan area network (MAN) is a network that interconnects users with computer resources in a geographic area or region larger than that covered by a local area network but smaller than the area covered by a wide area network. The term is typically applied to the interconnection of networks in a city into a single larger network (which may then also offer efficient connection to a wide area network). The amount of data traffic being sent over MANs is increasing at an exponential rate. This is due in part to the increasingly ubiquitous use of the Internet by consumers and businesses, as well as the increasingly bandwidth-intensive nature of the Internet applications that are being deployed.
An important aspect of MANs is the ability of MAN service providers to create virtual private network network connections (VPNs) across a single MAN infrastructure, referred to as a virtual metropolitan area network (VMAN). VMANs allow customers having multiple locations within a metropolitan area to transport private traffic, including virtual local area network (VLAN) traffic, over the shared single MAN.
However, the use of VMANs to handle traffic from multiple customers over a single MAN creates access and security issues. Therefore, it is important to segregate one customer from another so that there is no co-mingling of traffic.
In addition, customer traffic must be transported over the VMAN without interfering with the customers' own higher-layer protocols such as DECnet, or private IP subnets. For example, the DECnet Phase IV protocol can cause problems when routed to a Layer 2 MAN because the DECnet protocol changes the media access control (MAC) address in the packet's Layer 2, or Data Link layer, header. Since duplicate MAC addresses are typically not allowed, VMAN service providers end up managing DECnet streams by hand-something which neither the provider nor the customer wants.
The use of VMANs to handle traffic from multiple customers over a single MAN can also present scalability problems. For example, when switching VLANs based on the Institute for Electrical and Electronics Engineers (IEEE) 802.1Q standard, the traditional system-wide upper limit of VLANs that can be handled while maintaining complete 802.1Q interoperability is 4,096. This may be insufficient for MAN service providers that need to provide network services to buildings having large numbers of individual customers connected to the network via traditional layer-2 VLANs.
Accordingly, a new approach is needed to securely manage traffic in a VMAN network architecture which does not interfere with higher level protocols and which is highly scalable.